Don't MISS if you read the hole from certain FastHoley arrays.

src/ic/ic-compiler.cc

Index: src/ic/ic-compiler.cc
diff --git a/src/ic/ic-compiler.cc b/src/ic/ic-compiler.cc
index f597083e631be5e9aa49adcab9dbcf58a0225581..e25a3d9d1f6f60b0361bc3397687fde85b4d889f 100644
--- a/src/ic/ic-compiler.cc
+++ b/src/ic/ic-compiler.cc
@@ -110,7 +110,11 @@ Handle<Code> PropertyICCompiler::ComputeKeyedLoadMonomorphic(
 Handle<Code> PropertyICCompiler::ComputeKeyedLoadMonomorphicHandler(
     Handle<Map> receiver_map) {
   Isolate* isolate = receiver_map->GetIsolate();
+  bool is_js_array = receiver_map->instance_type() == JS_ARRAY_TYPE;
   ElementsKind elements_kind = receiver_map->elements_kind();
+  bool convert_hole_to_undefined =

[Jakob Kummerow, 2015/04/23 13:40:00]

Checking for a pristine array prototype is pointless here, because this is
compiled so early that it's pristine anyway, and the stub is doing the check,
right? Maybe add a comment about the latter, roughly:
// No need to check for an elements-free prototype chain here, the generated
// stub code needs to check that dynamically anyway.

[mvstanton, 2015/04/27 07:57:13]

That's right, and good idea to comment that. Done.

+      is_js_array && elements_kind == FAST_HOLEY_ELEMENTS &&
+      *receiver_map == isolate->get_initial_js_array_map(elements_kind);
   Handle<Code> stub;
   if (receiver_map->has_indexed_interceptor()) {
     stub = LoadIndexedInterceptorStub(isolate).GetCode();
@@ -122,9 +126,8 @@ Handle<Code> PropertyICCompiler::ComputeKeyedLoadMonomorphicHandler(
   } else if (receiver_map->has_fast_elements() ||
              receiver_map->has_external_array_elements() ||
              receiver_map->has_fixed_typed_array_elements()) {
-    stub = LoadFastElementStub(isolate,
-                               receiver_map->instance_type() == JS_ARRAY_TYPE,
-                               elements_kind).GetCode();
+    stub = LoadFastElementStub(isolate, is_js_array, elements_kind,
+                               convert_hole_to_undefined).GetCode();
   } else {
     stub = LoadDictionaryElementStub(isolate).GetCode();
   }